Method and apparatus for hardening gear teeth

ABSTRACT

An inductive heating assembly is provided comprising a support block having an upper and a lower supporting surface and a front wall. A plurality of inductor sectors each including a recess defined by an upper leg and a lower leg and a nose are mounted on the support block with the recesses receiving the block and with the legs overlapping the upper and lower surfaces, respectively, and the nose extending along the front wall. The nose is shaped to fit between adjacent gear teeth and means is provided for passing current in series through the legs and the nose of each sector.

United States Patent Inventors Appl. No.

Filed Patented Assignee George D. PfaiTman Farmington, Mich.;

Robert G. Armstrong, Chardon, Ohio 851,504

Mar. 20, 1969 Division of Ser. No. 558,087, June 16, 1966, Pat. No. 3,466,495

Jan. 12, 197 l Park-Ohio Industries, Inc.

Cleveland, Ohio a corporation of Ohio METHOD AND APPARATUS FOR HARDENING GEAR TEETH y 5 Claims, 15 Drawing Figs.

0.8. CI 2l9/l0.59, 219/1043, 219/1079, 266/4,148/147 Int. Cl 1105b 5/00, H05b 9/02 Field ofSearch 219/1059,

10.43last shoe, 10.79last shoe; 266/45; 148/147 [56] References Cited UNITED STATES PATENTS 2,848,363 8/1958 Clarcq, Jr. et al 148/147 2,857,154 10/1958 Jones I ,2 l9/10.59X 3,446,495 5/ 1969 Pfaflman et a1 266/4 Primary Examiner-A. Bartis Assistant Examiner-L. H. Bender Attorney-Meyer, Tilberry and Body ABSTRACT: An inductive heating assembly is provided comprising a support block having an upper and a lower supporting surface and, a front wall. A plurality of {inductor sectors each including a recess defined by an upper leg and a lower leg and a nose are mounted on the support block with the recesses receiving the block and with the legs overlapping the upper and lower surfaces, respectively, and the nose extending along the front wall. The nose is shaped to fit between adjacent gear teeth and means is provided for passing current in series through the legs and the nose of each sector.

PATENTED JAN I 2 l9?! SHEET 2 [IF 8 n rylll I INVENTQRS. GEORGE D, PFAFFMAN 8: ROBERT-G. ARMSTRONG WWW ATTORNEYS PATENTEU mu I 35554233 sum u or 8 FIG. 4

INVENTORS. GEORGE D. PFAFFMAN 8; ROBERT G. ARMSTRONG ATTORNEYS PATENTED JAN 1 2mm SHEEF 5 BF 8 INVENTORS. GEORGE D. PFAFFMAN 8a ARMSTRONG RQBERT e.

PATENTEUJAN1 2m sum 6 or 8 I B M V MV/ Z/ Wm INVENTORS 8 m M mm J N R FS T. M M R WA 06 T T.

@R a mo GR .24 25 26 (G) (c) (H) (c) (H) (C) PATENTED JAN 1 219?! SHEET 70F 8 INVEN'TOR.". GEORGE D. PFAFFMAN 8: ROBERT G. ARMSTRONG ATTORNEYS PATENTEDJANIZIHTI 3555.233

SHEET 8 OF 8 INVENTORS. GEORGE D. PFAFFMAN 8 ROBERT G 'ARMSTRONG ATTORNEYS METHOD AND APPARATUS FOR HARDENING GEAR TEETH This application is a division of applications Ser. No. 558,087, filed June 16, 1966, now US. Pat. No. 3,446,495.

METHOD AND APPARATUS FOR HARDENING GEAR TEETH The present invention pertains to the art of induction heating, and more particularly to a method and apparatus for hardening gear teeth by first inductively heating the teeth and then quenching them.

This invention is particularly applicable for use in hardening the inner, spaced teeth of a ring gear, and it will be described with particular reference thereto; however, it should be appreciated that the invention has much broader applications and may be used for hardening spaced teeth on the internal or external periphery of a gear. The term teeth is used herein to indicate spaced drive members, or similar protruding, reoccuring elements, and this term should not be considered as limiting the invention to any particular type of protruding, reoccuring elements.

In the manufacture of gears, it has become somewhat common practice to harden each tooth of the gear separately by first heating the tooth and then quenching it. The most widely accepted methodand apparatus for accomplishing this purpose includes an inductor unit which inductively heats either a tooth, or the facing surfaces of adjacent teeth, and then number oflteeth must be individually heated and quenched. In

addition, as succemive adjacent teeth on the periphery of a gear are hardened by prior method and apparatus, there is a The present invention is directed toward an improved" method and apparatus for hardening the spaced teeth of a gear whereby a plurality of gear teeth may be. simultaneously heated without causing substantial distortion of the gear during the hardening process.

In accordance with the present invention, there is provided an apparatus for hardening the spaced teeth of a gear having teeth arranged in a circle and on the periphery of a gear. This apparatus comprises an inductor means for simultaneously heating a selected number of alternate teeth in an arc sector extending along only a portion of the teeth circle: a quenching By hardening the spaced teeth of a gear in accordance with the apparatus and method defined above, the inductor means in effect moves twice around the gear and hardens alternate teeth the first time around the gear. The alternate unhardened teeth are hardened the second time around the gear. It is appreciated that in some cases the number of the teeth will require that the inductor means perform the hardening function by, in efi'ect, moving around the gear more than twice. In this case, and in accordance with another aspect of the invention, the inductor means includes at least two independently controlled inductors. One of the inductors may be turned off at the terminal end of the hardening cycle so that while the last group of teeth are being hardened, previously hardened teeth will not be annealed. This aspect of the invention will be described hereinafter in detail.

I The term altemate teeth" means spaced teeth having one or more teeth therebetween.

The primary object of the present invention is the provision of a method and apparatus for hardening gear teeth by using induction heating which method and apparatus limit distortion of the gear and decrease the time for hardening the teeth.

Another object of the present invention is the provision of a method and apparatus for hardening gear teeth by using induction heating which method and apparatus harden a plurality of alternate gear teeth simultaneously and then repeats this process until all teeth are hardened.

Still another object of the present invention is the provision of a method and apparatus for hardening gear teeth by using induction heating which method and apparatus uses an inductor means including at least two separately controlled inductors for heating a plurality of alternate teeth, as a group, with means for deenergizing at least one inductor to change the number of teeth being hardened.

Yet another object of the present invention is the provision of a novel inductor for heating a plurality of gear teeth, as a group, which inductor is easy to assemble and inexpensive to produce.

Still a further object of the present invention is the provision of a novel inductor for heating a plurality of gear teeth, as a group, which inductor is built up from a plurality of separate, somewhat identical sectors.

These and other objects and advantages will become apparent from the following description used to illustrate the preferred embodiment of the invention as read in connection with the accompanying drawings in which:

unit associated with the inductor means for quenching the heated teeth; means for indexing the gear to bring successive arc sectors along said circle into alignment with the inductor means; control means for causing the indexing means to index the gear a sufficient number of times and distances to heat and quench each of the teeth with a number of indexing times causing at least two revolutions of the gear with the alternate teeth that are unhardened during the first revolution being hardened during a subsequent revolution; means for causing relative movement between the inductor means and the gear in a direction axial of the gear before the gear is indexed to prevent interference between the teeth and inductor means; and, means for moving the inductor means into operative position with respect to the gear teeth after the gear is indexed.

In accordance with another aspect of the present invention, there is provided a method of hardening the spaced teeth of a gear which teeth are arranged in a circle. This method com.- prises the steps of inductively heating, as a group, a given number of alternate teeth, the group extending along only a portion of the teeth circle; quenching the heated teeth; and, repeating the heating and quenching steps at successive portions around the teeth circle until the circle has been circum scribed at least twice and all teeth have been heated and quenched.

FIG. 1 is a side elevational view showing somewhat schematically and in cross section the preferred embodiment of the present invention;

FIG. 2 is a top plan view illustrating, somewhat schematically, the preferred embodiment of the present invention;

FIG. 3 is an enlarged, partial side elevational view illustrating in more detail one aspect of the preferred embodiment;

FIG. 4 is an enlarged cross-sectional view illustrating another aspect of the preferred embodiment;

FIG. 5 is an enlarged cross-sectional view taken generally along line 5-5 of FIG. 4;

FIG. 6 is an enlarged top plan view illustrating the inductors used in the preferred embodiment of the invention;

FIG. 7 is a front elevational view of the inductor shown in FIG. 6;

FIG. 8 is an enlarged cross-sectional view taken generally along line 8-8 of FIG. 6;

FIG. 9 is an enlarged cross-sectional view illustrating another aspect of the preferred embodiment of the invention;

FIG. 10 is a top plan view of the gear being operated on by the present invention;

FIG. 11 is an enlarged top view illustrating the inductor used in accordance with the present invention;

FIG. 12 is a cross-sectional, bottom view illustrating the inductor shown in FIG. 1 1;

FIG. I3 is a three plane, cross-sectional view showing the various passageways within the inductor support block used in accordance with the present invention;

FIG. 14 is a schematic view illustrating the current path through the inductor used in accordance with the present invention; and,

FIG. 15 is a schematic view illustrating the stepping switch used in accordance with the present invention.

Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only and not for the purpose of limiting same, FIGS. 1 and 2 show an apparatus A for heating the internal, spaced teeth of ring gear B. The gear includes an outer flange 10, a mounting hub 12, and a number of spaced teeth 14 arranged in a circle. Apparatus A includes, primarily, a frame 20, a support table 22, best shown in FIG. 4, an indexing mechanism 24, best shown in FIGS. 4 and 5, a first heating unit 26, a second heating unit 28, and a heating unit moving mechanism, best shown in FIG. 1. Hereinafter there is a detailed description of these various elements and their functions with respect to the operation of apparatus A.

SUPPORT TABLE Referring now more particularly to FIG. 4, the support table 22 includes a base plate 40 having a dust shield, or cover 42. A bottom plate 44 is secured onto base plate 40 and supports a somewhat flexible top plate 46 having a downwardly extending hub 47. A plurality of spaced, support arms 48 are moved radially upon flexing of plate 46, in a manner to be described later. Each support arm 48 includes a vertically facing boss 50 and a horizontally facing boss 52. These bosses coact with the flange and hub 12 of gear B to locate the gear when the arms 48 are moved inwardly. In order to move the arms, there is provided a partition 54 between plates 44, 46. This partition defines a fluid chamber 56 in which there is provided a piston 58 connected onto the lower portion of hub 47. A fluid line 60 receives presurimd fluid through inlet 62. When pressurized fluid is forced into chamber 56, the arms 48 are extended radially, outwardly; and when the pressure is released, the arms flex radially, inwardly to grip the gear B. It is appreciated that various other arrangements could be provided for clamping the gear with respect to the table 22.

A lower fluid support 64 is secured onto a spindle 66 which is fixedly secured onto base plate 40. The spindle rotates in fluid support 64 and bearing 68, 70. A drive, or indexing, gear 72 is fixedly secured onto the spindle 66 for the purpose of rotating the support table by a mechanism which will be hereinafter described. The spindle and its rotating mechanism are enclosed within a housing 74 which is supported on a lower fixed plate 76.

INDEXING MECHANISM Referring again to FIG. 4, the indexing mechanism 24 includes an upper support block 80 and a lower support block 82 which generally define a chamber closed by an access cover 84. Within this chamber, there is provided a countershaft 86 joumaled within bearings 88, 90. A pinion gear 92 is fixedly secured to the upper end of shaft 86 so that it engages drive gear 72 to impart rotation to the drive gear when the shaft 86 is rotated. The opposite end of shaft 86 is splined for a purpose to be hereinafter explained. A shift rod 100 is reciprocated by a movable rod 101 which is controlled by a fluid cylinder 102 secured onto plate 104 at the lower support block 82. To guide rod 100 during vertical movement, there are provided axially spaced bearings 106, 108 fixedly secured onto support blocks 80, 82, respectively. A switch actuator 110, best shown in FIG. 1, is movable with rod 101. The actuator 110 is adapted to operate limit switch LS5 when the shift rod 100 is moved downwardly and limit switch LS7 when the rod is moved upwardly. These limit switches are supported on a plate 111.

Shift rod 100 supports a yoke 112 extending from sleeve 114 fixedly secured onto the rod. A first clutch member 116 has a groove 118 adapted to receive the bifurcated ends of yoke 112. At least two holes 120 are spaced around the member 116 for a purpose to be explained later. The clutch member 116 is reciprocally secured onto the splined end 94 of shaft 86 by a splined bore 122. As the rod is reciprocated, the clutch member 116 is moved vertically. A second clutch member 124 is provided below the first clutch member 116. This second clutch member includes a stub shaft 126 j'ournaled within bearings 128, 130.-'An,oil seal. 132 prevents unwanted oil leakage around the stub shaft.

Referring now to FIGS. 2, 4 and 5, there is provided, in accordance with the illustrated embodiment of the invention, an indexing rod extending generally perpendicularjto stub shaft 126. This rod is reciprocally mounted within bore 142 of housing 144. A rack portion 146, best shown'in FIG. 5, is provided on one side of the rod; and, the outer end of the rod 140 is adapted to abut an adjustable stop supported on plate 152. Referring more particularly to FIGS. 2 and'S, a fluid operated cylinder having a movable rod 162 with a rearward extension 164 is used to move the indexing rod 140. The rack portion 146 engages pinion 134 so that longitudinal movement of the rod rotates the second clutch member 124. A switch plate 166 is secured onto extension 164 so that forward movement of rod 162, and the extension 164, actuates limit switch LS8, and reverse movement of the rod and extension will actuate limit switch LS6.

Movement of the yoke 112 downwardly brings the clutch members 116, 124 into engagement with pins 136' of the second member being received within holes 120 of, the first member. When the clutch members are engaged, movement of rod 140 in a reverse direction will rotate a shaft 86 and, thus, the gear B. When the clutch members are disengaged, movement of the rod 140 in a forward direction conditions the mechanism for subsequent indexing. The purpose of this indexing function will be appreciated after the remainder of apparatus A is described.

HEATING UNITS (GENERAL) Referring to FIGS. 1, 2, 6 and 7, theseparately controlled heating units 26, 28 are schematically represented. In accordance with the illustrated embodiment of the invention, the inductor C of unit 26 is adapted to heat three alternate teeth, whereas the inductor D of unit 28 is adapted to heat two alternate teeth. Since the heating units 26, 28 are somewhat identical except for the separate inductors, only unit 26 will be described in detail. This description will apply equally to unit 28. Each unit includes a support plate 170 onto which is mounted a transformer 172. Primary power leads 174, 176, shown in FIG. 1, are directed to a terminal block 178.Secondary leads 180, 182 of unit 26, extend from the terminal block 178 and are connected to inductor C. In a like manner, secondary power leads 184, 186 extend from terminal block 178 and are connected onto inductor D.

INDUCTOR ASSEMBLY The inductor assembly 188 includes inductors C and D which are each supported for movement with the transformers 172 by support frame 190. Referring now to FIGS. 8, 11 and 12, the support frame 190 includes an inductor support block 192 having an upper surface 192 and a lower surface 192". Individual inductor sectors 194 include recesses 196 which allow each sector to be slipped over the support block 192. The recess is defined by legs 198, 200 and a nose 202. Each nose 202 includes a Carbonel E insert 204 on one side. The various sectors 194 are divided into pairs and the lower legs 200 of the two sectors forming a pair are connected at 206, as shown in FIG. 12. The connecting portion 206 is opposite from the sides of the sectors 194 which include the Carbonel E inserts. As will be explained later, the two sectors forming a pair are adapted to heat one tooth with the tooth extending between the sectors of the pair. The Carbonel E is used to prevent heating of the intermediate gear teeth which are not to be heated.

As shown in FIG. 11, the various pairs of inductor sectors are joined by connectors 120, 122, and 124. This provides an electrical circuit as shown in FIG. 14. Current flows from the generators through secondary leads 180, 182, 184 and 186 in a manner indicated by the arrows. As shown in this diagram, the inductor C includes six gear sectors 194 arranged into three pairs whereas the inductor D includes only four gear sectors arranged into two pairs. Current flow is determined by the connectors 220, 222, and 224. By viewing the wiring diagram, it is noted that the current flow in the nose portions 202 of adjacent gear sectors 194 in a particular pair is in opposite directions. This causes a high current flow in the tooth between the sectors of a given pair. The teeth which are positioned between pairs of gear sectors are subjected to current flow on opposite sides which is in the same direction. This current flow causes bucking currents in these teeth and has a tendency to cancel out the current flow in the intermediate teeth so that heating does not take place. It is appreciated that a number of pairs of gear sectors can be varied to change the number of alternate teeth being heated by the various induc- IOI'S.

In accordance with the present invention, the inductors C and D are independently controlled so that one may be turned off while the other is operative. In this manner, the inductor assembly 188 including both inductors C and D can either heat five alternate gear teeth, three alternative gear teeth, or two alternate gear teeth. Various combinations of two or more inductors with ditferent number of heated teeth and independently controlled power supplies can be used to change the number of gear teeth which may be heated by deenergizing certain specific inductors. The inductor sectors 194 are held onto the insulated block 192 by upper insulating pins 210 and lower insulating pins 212 which are received by recesses 211 of the inductor sectors. It is appreciated that various modifications may be made in the inductor sectors and their method of assembly without departing from the intended spirit and scope of this particular aspect of the invention.

INDUCTOR COOLANT SYSTEM To prevent overheating of the inductor and the power leads, a coolant system is provided which causes a coolant, such as water, to flow through the various elements making up the inductors. Essentially, a series of coolant systems are employed; however, before discussing these systems, the coolant paths through each pair of inductor sectors will be described. Refer ring to the inductor sector pair E best shown in FIGS. 9, 11 and 12, each sector pair includes an upper horizontal passage 230 in one sector 194. This passage communicates with a first or inlet nose passage 232 extending along the nose and ter rninating in a lower horizontal passage 234. As shown in FIG. 12, an inner connecting passage 236 in portion 206 forms a communication between passage 234 and a lower horizontal passage 238 of the second sector in the sector pair. Passage 238 terminates in a second or outlet nose passage 240 extend ing along the nose of the second gear sector. This passage 240 is communicated with an upper horizontal passage 242. These various passages form a continuous coolant path through each pair of gear sectors. The gear sector pair E has the outlet passage 242 communicated with the internal passage of corn nector 224. Each of the gear sector pairs includes this coolant system and the arrangement of these coolant systems is illustrated in FIG. 13. Nose passage 232 indicates the inlet sector of the sector pair, and passage 240 indicates the outlet sector of the sector pair.

Referring now more particularly to the inductor C for heat ing three alternate gear teeth 14, three separate coolant systems are employed. A coolant inlet 250, shown in FIG. I, is communicated with a conduit 252 extending along the lem 174. A transfer passage 254 in block 178 communicates the conduit 252 with an internal passage 256 within the secondary power lead 180. As shown in FIG. 11, coolant flows from the internal passage 256 into the first pair of gear sectors. After flowing through the sectors, the coolant flows out the conduits 258.

Referring now to the second coolant system in inductor C, an inlet 260, shown in FIG. 1, directs coolant to an internal passage 262 of secondary lead 182, in a manner similar to the first-mentioned coolant system. Coolant then flows through the second pair of inductor sectors and out conduit 264. The third coolant system includes an inlet conduit 270 which directs a coolant through the third pair of inductor sectors and out conduit 264. A partition 272 within connector 220 separates the conduits 258, 270. Of course, the conduits 258, 264 and 270 are insulated tubing which does not affect the electrical characteristics of the inductor C.

Referring now to inductor D, an inlet 280 shown in FIG. 2, introduces coolant into internal passage 282 of power lead 184, in a manner previously described. Thereafter, the coolant passes through the fourth pair of gear sectors and exits at outlet conduit 284. In a similar manner, coolant is introduced into passage 286 of lead 186 where it flows through the fifth pair of gear sectors and out the same conduit 284. It is appreciated that other coolant systems could be provided to cool the inductors C, D of apparatus A.

QUENCI-IING SYSTEM After the alternate teeth marked H in FIG. 11 have been heated, they are then quench hardened by introducing a quenching fluid, such as water or oil thereagainst. The system in apparatus A for accomplishing this purpose is best shown in FIGS. 8 and 13. A large inlet conduit 300 is communicated with angularly disposed passages 302, 304. These passages direct the quenching fluid into a relatively large plenum chamber 306 within block 192. A plurality of orifices 308 direct the quenching fluid from the plenum chamber 306 between the inductor sectors of' each sector pair. This is clearly shown in FIG. 13 wherein the previously heated teeth, or the spaces occupied thereby, are marked Q to indicate that they are subsequently quenched by the system described above. As seen in FIG. 8, a plurality of orifices 308 are provided between the sectors of a sector pair with the orifices being diverging to provide an even quenching pattern over the complete length of the previously heated teeth.

AIR SYSTEM The alternate teeth between the pairs of gear sectors are not heated when the inductors C, D are energized. To assure this, the Carbonel E inserts 204 are used to shield these teeth. To further assist in this function, apparatus A is provided with a system for blowing air against the teeth not being heated during the heating operation. Two separate air systems are employed. The first, or upper air system, is best shown in FIGS. 8 and 13, and it includes an upper inlet 310 directly commu nicated with a passage 312. This passage directs air into an upper plenum chamber 314. From here, the air is forced through orifices 316 against the teeth which are not being heated. In a like manner, a lower air blowing system is provided. This system is best shown in FIGS. 8, 12 and 13, and it includes an inlet 320 communicated directly with a passage 322. This passage introduces air into a plenum chamber 324 from which it is forced through orifices 326 against a lower portion of the altemate teeth not being heated. The air against the upper and lower portions of the teeth not being heated assist in preventing annealing of these teeth if they have previously been hardened. This function will be explained in more detail later.

HEATING UNIT MOVING MECHANISM The mechanism 30 for moving the heating units 26, 28 vertically with respect to gear B is best illustrated in FIGS. 1 and 2. The downwardly extending mounting plate 330 is coupled onto the support plate for the heating units. Fixedly L which coact with ways nt of the piste .i'l'h, onto plate 33th are secured onto plate arena 334 on frame Slit to uliow vertic l move and thus the heating un t switch actuators 3 th, .3 and When the plate is moved downwardly, the actuator closes n limit switch LS3. ts the moved upwardly, iimit switch M n the ct tor switch ljsl descrihed or in detail. A shroud or cove encioses a fluid-actuating 11" lets 362, 36 i and a. cylinde nected onto a mourning hrs means onto the tramc Zlitl'l. Also, motor Lonto plate s motor inciudcs a'u idea is pivotally conthe heating unit ing units are moved upwz with respect to gear retracted, the heatl umts i353, their heating positions.

lsU Cl'hTOlt ihi'ilEh iiilift Referring now to HUS "i curd it, the W with a locator assembly .Nll supporte by a trains ."hill locator assembly includes a downwnrdiy extending head A having a contoured nose adapted to he received between two is supported on a block 384 movabic with i 385 by means of oppositely which is shown it To vided an adjusting boit L nion 390 supported hy h pinto down of head Uepeudiuu 394 which a ates switci position, shown in tuli lii'lt there is provi" it 'v.

384 in the u position, the han- When the hlo A lWJ dle 396 is first moved to the then pulled around the c: phantom lines in 3. in is actuated. Consequently, i LSTl is actuated by the lo limit switch ltiili a tutti .,h Lon i switch trol the ope. iustrated einbodii 412 having run or are operated b operating push trolled lay a eludes cont,

A switch plate This plate includes words, the fir only when the s Thereafter, the energized.

The second heating it 12s contnolicd hy u meclian i l t "433 which tit) plate 4dr?) includes a peripheral cam 448 which extends between positions 1-10. The second heating unit, which heats two alternate gear teeth, is conditioned to'be energized when the stepping switch dill) is in position 1- 10. lnother words, the second heating unit 28 is conditioned to be on in the 10th position of the stepping switch, while the second heating unit is conditioned to be off. A; rcse't'relay Mill is olied by a contact When the cam'follower Md "ops oft 0% a 2m l, contact 432 is closed and reset-relay 45h is cucr izted. Reset l -"ti actuates mechanism $2 3 through a ed line. The function of this stepping Etit'lid in connection with the overall opera OPERATION The various structures explained above and their cooperative functions will be appreciated from the following description of the operation of apparatus A.

training to l, pressure is applied behind piston 58. This spa-ends support arm dd. Gear B is then placed into the spread anus and the locator 38th is moved into the downward position, shown in MG. The head 382 is forced between two adjacent teeth lid on the gear B. This aligns the gear for subsequent processing. ill/hen the locator is moved downwardly, plate 3 closes switch LS1. This causes pressure to be re lieved from chamber 56, and the arms 48 grip the gear 13 so that is it located with respect to the spindle so. Thereafter, the locator is moved upwardly. This trips limit switch LS2, as shown in MG. This limit switch then causes motor 360 to lower the heating units 26', 28. When the heating units are lowered, actuator 3 15) trips limit switch LS3, as shown in FIG. l, and the heating units 2365, are energized. Both heating it its energized since the stepping switch is in position no. i, and contacts @323, M2, shown in FIG. t5, are closed. The inductors C, D are in position shown in lFlG. o with the noses ll 2 ol each inductor sector W41 being between adjacent gear teeth ll i. previously explained, every other gear tooth is heated by current flow as shown in H6. M. After a preset time, the heating units are turned off and quenching fluid is directed through orifices This quench hardens the previously heated T hereafter, the quenching fluid is turned oh? and the inductors are raised by motor 35th. This moves the r late 33 h upwardly so that actuator 3 M trips limit switch Thereafter, die actuator 342 trips limit switch LS4. LS4; steps the stepping switch dllh into the next position, i.e. position no. 2. in this position, both heating units 26, 2% are conditioned to be turned on again.

ever-ting now hack to the operation of limit switch LSlltl. s swi causes 'lit rod ten to be moved downwardly by T The pins of second clutch member 12 3 reit? of first clutch member llllti. This engages to so that there is a direct drive between "t'if pinion W hen the shift rod lltltl) is moved to position, limit switch LS5, shown in FIG. ll, ed. Cylinder Shirt then retracts the indexing rod Mill to e right, shown in lFlG. 3. This rotates pinion 134i and pinion l. in this murmur, the gear B is rotated a preselected distance cwtermincd by the inwai'dinost position of rod lldll and the nount of tetra 'ng movement. This position is adjusted by l at one end of the rod Mill and stop 43% at the op- Jhcn throd Mt) has been retracted by cylinder I nlute Md trips switch LS6, shown in FIG. 2. This nu to moved upwardly. This disengages the clutch rnernhers llMi, 12%. When the shift rod Milli is in its upwzudrnost position, pin 4m moves into locating hole 462 to ioclc pla into another position. Of course, there are a number notes 4 i spaced circumterentially around the 1h. plate ll is rotated, in this embodiment, a rrespondiug to it) teeth so that the inductors heat ent group oi" alternate teeth. inc ro is in the upwardmost position, limit pped. This causes the indexing rod Mil to be moved forward against stop 150 so that it is conditioned for a subsequent indexing of the gear B. The forward movement of rod 140 causes plate 166 to trip limit switch LS8. This limit switch causes the inductors to again be lowered, and the cycle is repeated until 10 operations of the cycle have been completed. On the lOtn index, only inductor D is energized since only two teeth need be hardened during the last cycle. This will be explained later.

When the 10th cycle is completed, the reset relay 450 is energized which discontinues the operation of apparatus A and returns the stepping switch to position 1. At this time, the gear is released and may be removed. it is appreciated that various hydraulic and electrical circuits have been eliminated from this disclosure for the purposes of simplicity. Various electrical and hydraulic circuits could be adapted for use with apparatus A by a person with ordinary skill in this particular an.

Referring now to FIG. 10, a particular gear B is illustrated. This gear has 47separate teeth. In the first position of the steppingswitch, the teeth labeled A (teeth 1, 3, 5, 7 and 9) are hardened. In the second position, the teeth labeled B are hardened. Each time the gear B is indexed in the direction of the arrow in FIG. l 10 different teeth are brought into operating position with respect to the inductors C, D. This hardening of alternate teeth is repeated in accordance with the letters above the various numbered teeth. The inductors C and D remain stationary with respect to the gear B, and the teeth hardened by inductor C are marked Y, while the teeth hardened by inductor D are marked X. As the hardening operation progresses from one group of teeth to another the ninth position of the gear hardens the teeth designated I. Thereafter, only teeth 44 and 46 have not been hardened. The stepping switch has progressed through nine separate steps and has hardened 45 teeth. As the gear is indexed to the 10th position, the inductor C is turned 05. Consequently, the inductor D hardens teeth 44 and 46 to complete the hardening of all teeth around the periphery of gear B. It is appreciated that as the number of teeth of a gear varies, the number of indexes may vary and the particular heating station turned otT' may be different. 'In addition, the inductors may heat a different number of teeth when desired. By heating only altemate teeth at one time, warpag'ind distortion of the gear is reduced. In addition, the apparatus A hardens a number of teeth at one time. This substantially reduces the overall cycle time for inductively heating and then quenching the individual teeth around the periphery of the gear B.

The present invention has been described in connection with one limited embodiment of the invention; however, various changes may be made in this embodiment without departing from the intended spirit and scope of the present invention as defined in the appended claims.

We claim:

1. An inductor assembly for inductively heating a plurality of gear teeth arranged in a circle, said inductor assembly comprising:

a. a support block having an upper and a lower supporting surface and a front wall;

b. a plurality of inductor sectors each including a recess defined by an upper leg, a lower leg, and a nose, said sectors being slidable onto said support block with said recess receiving said block, with said legs overlapping said surfaces, respectively, and said nose extending along said wall;

c. said nose being shaped to fit between adjacent teeth;

, d. means for passing current in series through said legs and said nose of each sector; and

e. means for locking said sectors onto said block.

2. An inductor assembly as defined in claim 1 wherein said sectors are divided into pairs and said lower legs of the two sectors of each pair are electrically joined.

3. An inductor as defined in claim 1 wherein said locking means includes elements extending from said block into locking en ement with the le of the inductor sectors.

4. An in uctor assembly as efined in claim 3 wherein said elements are removable pins.

5. An inductor assembly as defined in claim 1 wherein said sectors are arranged in pairs with the adjacent legs of the two sectors in each pair being electrically connected, and said current passing means including a first set of power leads connected to one group of sector pairs and a second set of power leads connected to another group of said sector pairs. 

1. An inductor assembly for inductively heating a plurality of gear teeth arranged in a circle, said inductor assembly comprising: a. a support block having an upper and a lower supporting surface and a front wall; b. a plurality of inductor sectors each including a recess defined by an upper leg, a lower leg, and a nose, said sectors being slidable onto said support block with said recess receiving said block, with said legs overlapping said surfaces, respectively, and said nose extending along said wall; c. said nose being shaped to fit between adjacent teeth; d. means for passing current in series through said legs and said nose of each sector; and e. means for locking said sectors onto said block.
 2. An inductor assembly as defined in claim 1 wherein said sectors are divided into pairs and said lower legs of the two sectors of each pair are electrically joined.
 3. An inductor as defined in claim 1 wherein said locking means includes elements extending from said block into locking engagement with the legs of the inductor sectors.
 4. An inductor assembly as defined in claim 3 wherein said elements are removable pins.
 5. An inductor assembly as defined in claim 1 wherein said sectors are arranged in pairs with the adjacent legs of the two sectors in each pair being electrically connected, and said current passing means including a first set of power leads connected to one group of sector pairs and a second set of power leads connected to another group of said sector pairs. 